cmm

#### Rules for Manual Scans in General

Do manual scans should along the machine axis (the X, Y, or Z axis):

Suppose that your part requires a scan along the surface of a sphere. To do this scan:

1. Lock the Y axis. This is done by using a lock switch on your CMM. You can set this switch to ON/OFF to prevent or allow movement in a particular axis.

2. Begin scanning in the +X direction.

3. Unlock the Y axis, and move to the next row along +Y or -Y.

4. Lock the Y axis again.

5. Scan back in the reverse (-X) direction.

When you do multiple rows of manual scans, we recommend that you reverse every other scan line. The internal algorithms depend on this kind of regularity and could give poor results if the scheme is not followed.

1. Begin the scan along the surface in the +X direction.

2. Move to the next row, and scan along the -X axis.

3. Continue to switch the direction of the scan as needed.

Compensation Limitations

PC-DMIS automatically takes hits in a three-dimensional manner whenever you perform supported manual scans using a hard probe.

With Fixed Distance, Fixed Time / Distance, and Fixed Time scans, PC-DMIS automatically takes manual hits in a three-dimensional manner in any direction. This is useful when scanning using free moving manual CMMs (such as a Romer or Faro arm) whose axes cannot be locked.

Since you can move the probe in any direction, PC-DMIS cannot accurately determine the proper probe compensation (or the Input and Direction vectors) from the measured data.

There are two solutions to the compensation limitations:

- If CAD surfaces exist, then you can select FINDNOMS from the Nominals list. PC-DMIS attempts to find the nominal values for each measured point in the scan. If the nominal data is found, then the point is compensated along the found vector, allowing proper probe compensation. Otherwise, it remains at Ball Center.

- If CAD surfaces do not exist, then probe compensation does not occur. All data remains at Ball Center.